This project involves a study of the cell and molecular biology of human retinal epithelium using tissue culture techniques. We shall develop a serum-free media for maintaining these cells in culture. We shall study the biochemistry of vitamin A that may be especially unique to these cells. This includes examination of the carrier and receptor mediated uptake and distribution of vitamin A in these cells and the esterification, ester hydrolysis and cis-trans isomerization of vitamin A. We shall attempt to understand why these cells release their large stores of vitamin A shortly after they are placed in culture and pursue this problem by in vivo experiments in owl monkeys by following the vitamin A content of retinal epithelial cells after neural retinal detachment. We shall use the same primate model to examine the long term fate of cultured human retinal epithelial cells that have been labeled with tritiated thymidine and subsequently transplanted to denuded Bruch's membrane of the host monkey's retina. We shall attempt to reattach the neural retina to these transplanted epithelial cells. The research is relevant to understanding the unique biology and biochemistry of normal human retinal epithelial cells and their interactions with the neural retina. It can also be useful for understanding and possibly treating abnormalities in this cell layer due to genetic or toxic factors.